Mold bond release coating of pva and lignitic sulphite waste



April 1968 R. W. CHILDERS ETAL- 3,376,240

MOLD BOND RELEASE COATING OF PVA AND LIGNITIC SULPHITE WASTE Filed Nov.17, 1966 WJW United States Patent 3,376,240 M'OLD BOND RELEASE COATING(PF PVA AND LIGNITIC SULPHITE WASTE Robert W. Childers, Tulsa, Okla, andRichard K. Snow, Westwood, N.J., assignors to Raymond International Inc,New York, N.Y., a corporation of New Jersey Continuation-impart ofapplication Ser. No. 429,018, Jan. 29, 1965. This application Nov. 17,1966, Ser. No. 602,440

9 Claims. (Cl. 260-175) ABSTRACT OF THE DISCLOSURE The followingspecification describes a composition made up of lignitic wastematerial, polyvinyl alcohol, and

water in special proportions for use as a concrete to mold.

release coating. The specification also describes a method of formingtextured concrete surfaces by the use of the coating to retard surfacecuring followed by surface vwashing.

The foregoing Abstract of the Disclosure is solely for the purpose ofenabling the Patent Ofiice and the public generally to determine quicklyfrom a cursory inspection the nature and gist of the technicaldisclosure,

designed for repeated reuse in the production of cast-inplace concreteshapes, and has for its object the elimination or minimization ofadherence between the molding form and the concrete after the latter hasset to permit removal of the form.

The invention has for its objects the provision of a novel coatingcomposition and method of treating such forms, for achieving substantialfreedom from adherence of the moldin shape to the concrete on setting,with resultant smoothness and freedom from flaws of the finishedconcrete shape and with no impairment chemically or structurally of theconcrete surface.

When liquid concrete is poured Within, about or against a molding formfor imparting a desired shape, considerable difiiculty is encountered inremoving the mold form after the concrete has set, due to sticking oradherence of the solidified concrete to the mold surface engaging thesame. In an effort to eliminate this difficulty, it has heretofore beenproposed to precoat the mold surface against which the concrete is cast,with various coating compositions such as mineral oils of various typesand viscosities, water-in-oil emulsions and other oleaginous substancesimmiscible with water; also with various metal or organic salts of bothinorganic and organic acids, and various complex organic compounds orcomplexes, none of which, however, has effectively solved this problem.

What might be termed the acid test as to the effectiveness of a releasecoating composition for purposes aforesaid, is encountered in theformation in the ground of cast-in-place tubular concrete pile shells.Such shells are conventionally placed by driving into the ground to3,376,240 Patented Apr. 2, 1968 a desired depth of penetration, atubular metal casing assembled on a booth plate or driving point. Afterthe driving is complete or prior thereto if desired, a closedcylindrical metal form or mandrel of substantially smaller diameter thanthe casing is concentrically inserted therein until it rests upon thebooth plate, and the annular space between the casing and mandrel filledwith liquid concrete. The outer casing is then withdrawn before theconcrete has set so that no serious problems of adherence of theconcrete to the casing are encountered, The mandrel, however, cannot bewithdrawn until the concrete has solidified sufiiciently to retain itsshape, andhence tends strongly to adhere to the mandrel throughout itssurface area, requiring tremendous pulling forces for withdrawal of themandrel. Release coating compositions as heretofore proposed, includingthose above mentioned, have proved of little value in reducing thisadherence.

We have, however, evolved a release coating composition which has provedhighly effective for such and related applications, and such thatadherence between the solidified concrete shell and the mandrel issubstantially nil, permitting the mandrel to be easily withdrawn, andleaving the shell interior with a smooth surface, free from flaws andunchanged as to the ultimate chemical or physical structure as comparedto the concrete in the remainder of the shell.

The release coating composition of our invention comprises the reactionproduct in boiling water of polyvinyl alcohol (PVA) and the ligniticwaste from sulphite paper manufacture. This lignitic Waste isessentially sulphonated lignin or more specifically acalcitun-ligno-sulphonate complex. A suitable grade of polyvinyl alcoholis one having a viscosity of 24-28 centipoises, a hydrolysis of 99.85%plus, a pH of 5.5-7.5, with volatiles of 5% maximum and ash of 2%maximum.

The preferred proportions of the make-up are about 50 grams by weight ofdry 'PVA, and grams of lignin complex to 500 grams of water. Tests havebeen conducted to establish the operative limits within which theseproportions may be varied. These tests have shown that the most criticalcomponent of the make-up is the PVA concentration, due to its effectupon resulting viscosity. Where the PVA concentration is less than 6.25%(weight of dry PVA to total weight of solution), the mixture isincapable of supporting itself on a form; and will simply run offcarrying the lignin with it, so that no concrete release characteristicsare obtained. Where, on the other hand, the PVA concentration exceeds12% the mixture becomes 'so jelly-like that it is incapable of beingspread on the form.

Thus, compositions according to the present invention include 40-75parts by weight PVA and l0050 parts by weight of the lignin complex to500 parts by weight of water.

The procedure for making the coating composition of the invention is toheat the water to boiling and then add the lignin complex whichapparently goes into solution or into extremely finely comminutedsuspension. After solution or suspension of the lignin complex iscomplete, the day PVA is added which also appears to go into solution orfinely dispersed suspension. Applicants have been unable to determinewhether or not a true chemical reaction is here involved; however, thePVA may be added first, or dry PVA is added which also appears to gointo solution and then added to the solution simultaneously.

In the coating composition as thus produced, the lignin complex appearsto act as a retarder which slows up the hardening of the concrete at themold-concrete interface, thereby to prevent a bond between the concreteand the mold. A satisfactory film coating cannot, however, be obtainedwith this constituent alone in aqueous medium. Hence it was foundnecessary to incorporate therewith a suitable film forming carrier todissolve or suspend the retarder in order to distribute the retarder inthe concrete, for which purpose the PVA proved highly effective as thefilm forming agent.

The release coating composition produced as above may be applied to themetal, wood, plastic or other mold surfaces by brushing, spraying orrolling techniques. The exact action of the so-coated material is notcompletely understood. Observations have established, however, thatessentially what happens is that a continuous dry film is obtained onthe mold surface which becomes soft, elastie and slick upon contact withthe wet concrete. This film then acts as a lubricating and separatinglayer between the concrete and mold and permits a ready separation. Thefilm separates from both mold and concrete and either is brought to thesurface along with the mandrel as applied to the production of a castin-place concrete shell or, alternatively, falls to the bottom of thehole. in the concrete.

There does, however, appear to be a reaction between the coatingmaterial and the concrete. This reaction creates a water insoluble,continuous film which is soft, elastic and slick to the touch. Thesecharacteristics then allow the film to act as a lubricating layerbetween the concrete and metal.

The invention resides in the selection and combination of the twoingredients for the coating material. Neither the retarder or filmformer will provide a satisfactory separation by itself. Together theyprovide complementary functions and accomplish the desired releasingaction.

By way of illustrating the invention as applied to the placement in theground of a cast-in-place concrete shell, reference will now be had tothe annexed drawing where- FIGURE 1 is a view in axial sectionalelevation of a pile driving assembly being driven into the ground, andcomprising an outer tubular casing, a centrally disposed mandrel,disposed on a boot plate together with a driving head, the mandrelhaving been precoated with the release coating composition of theinvention. FIGURE 2 is a similar view after completion of the drivingwith the driving head removed and showing the filling of the annularspace between the mandrel and the casing with liquid concrete. FIGURE 3is a similar view but showing the casing in the process of beingwithdrawn while the concrete remains liquid. FIGURE 4 is a similar viewbut with the casing fully withdrawn and after the concrete has hardenedand set, showing the withdrawal of the centrally disposed mandrel.

and centrally disposed mandrel 11 of substantially small-' er diameter,are mounted on a boot plate or driving point 12, and the assembly driveninto the ground 13 by means of a driving head 14 surmounting the casing.The mandrel, as stated, has been precoated with the aforesaidlignopolyvinyl alcohol coating composition of the invention, asindicated at 12a. Referring to FIG. 2, upon completion of the driving,the driving head 14 is withdrawn, and the annular space between thecasing and mandrel 11 is filled with liquid concrete, as at 15, suppliedthereto from a grout line 16 extending to the top of the casing asshown. Referring to FIG. 3, after the annular space between the casing10 and mandrel 11 has been filled with liquid concrete substantially tothe ground line 17 as shown, the casing 10 is withdrawn, allowing theliquid concrete to flow against the surrounding earth 13 as at 18.Referring to FIG. 4, after the tubular concrete shell 15 has hardenedand set, the mandrel 11 is withdrawn as 4 shown, to leave in the ground13 the now fully hardened and cast-in-place concrete shell resting onthe booth plate 12. As above explained, the release coating composition12a permits of easy withdrawal of the mandrel without appreciableadherence to the hardened concrete shell.

Tests have shown that the PVA concentration in addition to controllingthe viscosity of the composition also directly affects the thickness ofthe resulting film. Thus where, as above described, pile forms are used,a relatively large concentration of the PVA should be employed. This isbecause the pile forms are removed, not by backing them off the concretesurface, but instead by sliding them up along the concrete surface ofthe pile. Accordingly a relatively thick lubricating film (formed by thehigh PV concentration), is needed. Where, on the other hand, theconcrete forms are of the type which can be removed by backing them otfthe formed concrete sur face, then the thick lubricating film is notrequired. 'In such case the PVA operates primarily to maintainviscosity, so that the lignin complex will remain in suspension and willbe distributed over the concrete.

Tests have also shown that the lignin concentration affects theviscosity of the overall composition only slightly; and that its primaryeffect is to control the duration of hardening of the portion of theconcrete with which it is in direct contact.

It has been possible, by means of the present invention, to produceunusual textured effects upon concrete surfaces. This is achieved bycontrolling the lignin concentration so that a preselected amount ofcuring retardation is achieved. Thereafter, forms are arranged with thecomposition spread thereon and concrete is poured into the forms. Theforms are held in place until the concrete is basically set. .At thispoint the forms are removed. The portion of the poured concrete whichwas immediately adjacent the forms is not fully hardened at this pointdue to the retardation effect of the lignin. The concrete surface isthen hosed down with water which washes away the unhardened cement andunsecured stone, gravel and sand portions near the surface. As a resultthe remaining surface will take on a textured appearance caused by theexposed portions of stones and gravel held in place by the inner regionsof the concrete unaffected by the re tarding action of the lignincomplex.

This last described technique is made practical through the compositionof the present invention for the composition, while containing lignin, aknown staining agent, does not stain the concrete. This is because thefilm which results from the use of the composition in addition toperforming as a releasing and lubricating agent, also serves to pull offfrom the concrete all lignitic material so that a clean concrete surfaceis produced.

According to a further feature of the invention the release coating ismade even more effective by using the composition as a vehicle tosupport finely produced aluminum. The aluminum is thus held in intimatecontact with the concrete and reacts with the concrete during thehardening thereof to evolve hydrogen gas. This gas expands and serves toenhance the separatingcharacteristics of the composition so that theform may be even more readily removed from the concrete surface. It hasbeen found that about 20-100 grams of finely ground aluminum powdermixed thoroughly into the above described compositions will operate toprovide thisaddi tional release function in a satisfactory manner.

What is claimed is:

1. A coating composition consisting essentially of the reaction productin boiling water of polyvinyl alcohol and lignitic waste material in theproportions of about 4075 grams (dry weight) of said alcohol and 100grams of said waste material per 500 grams of water.

2. A coating composition as in claim 1 wherein said lignitic wastematerial is waste material from the sulphite paper process.

3. A coating composition as in claim 1 wherein said lignitic wastematerial comprises sulphonated lignin.

4. A coating composition as in claim 1 wherein said lignitic wastematerial is calcium-ligno-sulphonate.

5. A coating composition as in claim 1 wherein said polyvinyl alcohol ispresent in a concentration between 6.25 and 12 percent of the totalweight of the composition.

6. A coating composition as in claim 1 wherein said composition consistsessentially of 50 grams of said polyvinyl alcohol and 100 grams of saidlignitic waste material for each 500 grams of water.

7. A coating composition as in claim 1 wherein said composition includesaluminum material.

8. A coating composition as in claim 1 wherein said composition includesfinely divided aluminum powder.

9. A coating composition as in claim 1 wherein said composition includesfrom 20-100 grams of finely divided aluminum powder per 500 grams ofWater.

References Cited UNITED STATES PATENTS 2,579,481 12/1951 Fenn 26017.52,954,353 9/1960 Bruce et al 26017.5 3,115,414 12/1963 Lott-ridgs et a1.10638.23 3,198,640 8/1965 Walsh et al. 10638.3 3,144,690 8/ 1964Buckingham l06-38.9

FOREIGN PATENTS 633,710 12/1949 Great Britain.

15 WILLIAM H. SHORT, Primary Examiner.

J. NORRIS, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,376,240 April 2, 1968 Rboert W. Childers et a1.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 2, lines 63 and 64, "or dry PVA is added which also appears to gointo solution" should read or the PVA and lignin solids may be firstmixed together Column 4, line 15, "PV" should read PVA Column 5, line 2,"comprises" should read is Signed and sealed this 12th day of August1969.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Attesting Officer Commissioner of Patents WILLIAM E. SCHUYLER, JR.

